EP0890656B1 - Procédé de nitruration de surfaces de pièces métalliques - Google Patents

Procédé de nitruration de surfaces de pièces métalliques Download PDF

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Publication number
EP0890656B1
EP0890656B1 EP98108307A EP98108307A EP0890656B1 EP 0890656 B1 EP0890656 B1 EP 0890656B1 EP 98108307 A EP98108307 A EP 98108307A EP 98108307 A EP98108307 A EP 98108307A EP 0890656 B1 EP0890656 B1 EP 0890656B1
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EP
European Patent Office
Prior art keywords
nitrogen
workpieces
nitriding
gas atmosphere
nitrogen content
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP98108307A
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German (de)
English (en)
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EP0890656A1 (fr
Inventor
Jan Willem Bouwman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ipsen International GmbH
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Ipsen International GmbH
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding

Definitions

  • the invention relates to a method for embroidering the edge layer metallic workpieces in a nitrogenous gas atmosphere at a Temperature between 1000 ° C and 1200 ° C.
  • thermochemical treatment of a metallic workpiece Enriching the surface layer with nitrogen is very different Embodiments known.
  • the stated goal here is through a Diffusion saturation of the surface layer with nitrogen the material properties such as hardness, wear resistance, fatigue strength or Improve corrosion resistance. This is how nitriding in one Temperature range of ⁇ 600 ° C the boundary layer by excretion of Nitrides hardened.
  • the heat treatment parameters for the nitriding process depend on the alloy composition of the base material. They must be chosen so that the desired nitrogen enrichment in the surface layer occurs without the nitrogen solubility limit being exceeded.
  • the main process parameters are the temperature, the composition and the pressure of the gas atmosphere, which contains the nitrogen, as well as the treatment time for the required nitriding depth.
  • Ammonia is often used as the nitrogen-releasing medium, since the NH 3 molecules disintegrate immediately in a temperature range above 1000 ° C.
  • EP 0 652 300 A1 describes a process for the heat treatment of near-net shape parts known from stainless steel, in which by Embroidery at a temperature between 1000 ° C and 1200 ° C in one nitrogen-containing gas atmosphere and a subsequent cooling austenitic surface layer with more than 0.3% by weight of dissolved nitrogen is formed.
  • the upper limit for the nitrogen content is the beginning nitride excretion determined. The subsequent cooling occurs so quickly that there is no nitride excretion during this period occurs.
  • the well-known process makes it high-strength and tough austenitic surface layer created over a ductile core, whereby by the diffusion of nitrogen also the austenitic structure in the Surface layer is stabilized so that martensitic or ferritic Structural components in the peripheral zone can also be converted to austenite, which leads to leads to an increase in wear resistance.
  • Another disadvantage of the known method is that the difference in concentration in nitrogen content between marginal and Core area is extremely small, so a long treatment period is necessary to achieve a specified nitriding depth.
  • a disadvantage of the known method is the poor reproducibility of a same nitrogen content as well as the resulting large scatter of Nitrogen absorption within a batch of workpieces.
  • the invention has for its object to develop a method of the type mentioned in such a way that, while avoiding the disadvantages described, a nitrogen content corresponding to the arithmetic specifications is achieved with a simultaneously reduced treatment time.
  • the invention is based on the surprising finding that one with the Zheng prediction model that forms the current state of knowledge (Zheng X .: Nitrogen Solubility in Iron-Base Alloys and Powder Metallurgy of High Nitrogen Stainless Steels, thesis ETH Zurich No. 9488, Zurich, 1991) calculated equilibrium specifications corresponding nitrogen content can be achieved if the partial pressure of nitrogen initially above necessary equilibrium pressure is set and only in a second Level that for the required nitrogen content of the existing Workpiece material necessary equilibrium pressure corresponds.
  • the duration of the first and second Process section depending on the workpiece material used and the required nitrogen content of the rim chosen to be high To achieve reproducibility. It has proven to be particularly advantageous exposed the workpieces during the first and second Expose process section to the same treatment duration.
  • the workpieces are before the actual embroidery under vacuum to the embroidery temperature heated to contribute to the formation of nitrides on the surface of the workpieces avoid lower temperatures.
  • the workpieces in Connection to the embroidery can be deterred, so that depending on used workpiece material a corrosion-resistant surface layer a fully austenitic or martensite structure is created.
  • the Cooling rate chosen while avoiding nitride precipitation becomes.
  • Gas is advantageously used for quenching, so that a Carburizing the surface layer compared to, for example Oil quenching must be ruled out.
  • the gas be with an excess pressure is applied.
  • workpieces are not made from rusting austenitic, martensitic, ferritic, ferritic-austenitic or ferritic-martensitic steel is used so that Nitrogen as a further alloying element to increase the strength of the Boundary layer and leads to an increase in corrosion resistance.
  • Vacuum furnace is used to make variable changes in process parameters and the type of treatment.
  • the current state of knowledge appropriate embroidery processes the temperature and pressure of the Nitrogen kept constant over the treatment period. This will put pressure and temperature depending on the desired nitrogen content set by the choice of alloy composition of the used workpiece and in this regard thermodynamic equilibrium is given.
  • the current one State-of-the-art method for calculating the process parameters Temperature and nitrogen partial pressure come from Zheng (Zheng X .: Nitrogen Solubility in Iron-Base Alloys and Powder Metallurgy of High Nitrogen Stainless Steels, thesis ETH Zurich No. 9488, Zurich, 1991).
  • the one with the Nitrogen atmosphere in equilibrium Workpiece surface takes according to Fick's second law of diffusion as illustrated schematically in FIGS. 2 and 2a. At the Workpiece surface in constant equilibrium Process size, the penetration depth of nitrogen depends essentially on the Length of treatment.
  • Fig. 2b are those using the method according to the invention values of nitrogen content in the surface layer of a workpiece those using the known method as an example juxtaposed.
  • the material used in the present example is a stainless steel of material number 1.4462, which is used as a batch of workpieces was embroidered in a vacuum oven at a temperature of 1150 ° C. To achieve the nitrogen temperature, the one with the Batch loaded vacuum furnace with a residual pressure of less than Evacuated 0.1 mbar and then heated with intermediate rinsing. To the conventional method was then embroidered for 15 hours in a pure nitrogen atmosphere with a constant pressure of 220 mbar, the at the specified temperature of 1150 ° C and the used Material corresponds to the equilibrium pressure on the workpiece surface.
  • the nitrogen pressure was during the first seven and a half hours to a constant 660 mbar and thus far above the necessary equilibrium pressure of 220 mbar.
  • a Treatment duration of 15 hours was both that of conventional Method as well as those embroidered on by the method according to the invention Workpiece batches of pure nitrogen quenching at one pressure of about 6 bar.
  • the method according to the invention was used achieves a nitrogen content of approx. 0.67% by weight on the workpiece surface, while according to the conventional method only a value of approx. 0.42 % By weight was to be achieved.
  • This difference continues inside the Workpiece, with a penetration depth of 2 mm the nitrogen content still almost twice as high by the method according to the invention was like that according to the conventional method and also - as Fig. 2a to remove is - almost corresponds to the calculated course.
  • the process according to the invention not only the nitrogen content increases, but at the same time also the penetration depth constant treatment time of 15 hours was increased.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Automatic Embroidering For Embroidered Or Tufted Products (AREA)

Claims (10)

  1. Procédé destiné à la nitruration de la couche superficielle de pièces métalliques dans une atmosphère de gaz contenant de l'azote à une température comprise entre 1 000 °C et 1 200 °C,
       caractérisé en ce que,
    pour l'obtention d'un potentiel azote en excédent dans l'atmosphère de gaz, la pression partielle de l'azote dans l'atmosphère de gaz est réglée pendant la nitruration, dans une première phase de procédé au-dessus d'une pression d'équilibre, et dans une deuxième phase de procédé égale à cette pression d'équilibre,
    la pression d'équilibre correspondant à l'équilibre thermodynamique entre l'atmosphère de gaz et la surface de la pièce à traiter, calculé pour le matériau de la pièce à traiter, et à une teneur en azote prescrite de la couche superficielle, et
    les durées de la première et de la deuxième phase de procédé étant choisies en fonction du matériau et de la teneur en azote souhaitée de la couche superficielle.
  2. Procédé selon la revendication 1, caractérisé en ce que les pièces sont exposées pendant la première et la deuxième phase de procédé à une même durée de traitement.
  3. Procédé selon la revendication 1 ou 2, caractérisé en ce que, avant la nitruration proprement dite, les pièces sont portées sous vide à la température de nitruration.
  4. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce que les pièces sont trempées après la nitruration.
  5. Procédé selon la revendication 4, caractérisé en ce que la vitesse de trempe est choisie afin d'éviter une précipitation de nitrures.
  6. Procédé selon la revendication 4 ou 5, caractérisé en ce que du gaz est utilisé pour la trempe.
  7. Procédé selon la revendication 6, caractérisé en ce que le gaz est sous surpression.
  8. Procédé selon l'une quelconque des revendications 1 à 7, caractérisé par des pièces en acier inoxydable austénitique, martensitique, ferritique, ferritique-austénitique ou ferritique-martensitique.
  9. Procédé selon l'une quelconque des revendications 1 à 8, caractérisé par une atmosphère de gaz en azote pur.
  10. Procédé selon l'une quelconque des revendications précédentes, caractérisé par un four à vide destiné à la mise en oeuvre du procédé.
EP98108307A 1997-07-12 1998-05-07 Procédé de nitruration de surfaces de pièces métalliques Expired - Lifetime EP0890656B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19729984A DE19729984A1 (de) 1997-07-12 1997-07-12 Verfahren zum Aufsticken der Randschicht metallischer Werkstücke
DE19729984 1997-07-12

Publications (2)

Publication Number Publication Date
EP0890656A1 EP0890656A1 (fr) 1999-01-13
EP0890656B1 true EP0890656B1 (fr) 2001-06-20

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Family Applications (1)

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EP98108307A Expired - Lifetime EP0890656B1 (fr) 1997-07-12 1998-05-07 Procédé de nitruration de surfaces de pièces métalliques

Country Status (3)

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EP (1) EP0890656B1 (fr)
AT (1) ATE202385T1 (fr)
DE (2) DE19729984A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011077368A1 (de) 2011-06-10 2012-12-13 BSH Bosch und Siemens Hausgeräte GmbH Haushaltsgerät mit einem wärmebehandelten Haushaltsgeräte-Bauteil
DE102011105426A1 (de) * 2011-06-22 2012-12-27 Mt Aerospace Ag Druckbehälter zum Aufnehmen und Speichern von kryogenen Fluiden, insbesondere von kryogenen Flüssigkeiten, und Verfahren zu dessen Herstellung sowie dessen Verwendung

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106637059B (zh) * 2016-12-21 2019-03-05 机械科学研究总院青岛分院有限公司 一种低温气体渗氮的催化方法
CN106637058B (zh) * 2016-12-21 2019-06-25 机械科学研究总院青岛分院有限公司 一种奥氏体不锈钢的低温气体渗氮方法

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4333917C2 (de) * 1993-10-05 1994-06-23 Hans Prof Dr Ing Berns Randaufsticken zur Erzeugung einer hochfesten austenitischen Randschicht in nichtrostenden Stählen

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011077368A1 (de) 2011-06-10 2012-12-13 BSH Bosch und Siemens Hausgeräte GmbH Haushaltsgerät mit einem wärmebehandelten Haushaltsgeräte-Bauteil
DE102011105426A1 (de) * 2011-06-22 2012-12-27 Mt Aerospace Ag Druckbehälter zum Aufnehmen und Speichern von kryogenen Fluiden, insbesondere von kryogenen Flüssigkeiten, und Verfahren zu dessen Herstellung sowie dessen Verwendung
DE102011105426B4 (de) * 2011-06-22 2013-03-28 Mt Aerospace Ag Druckbehälter zum Aufnehmen und Speichern von kryogenen Fluiden, insbesondere von kryogenen Flüssigkeiten, und Verfahren zu dessen Herstellung sowie dessen Verwendung

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Publication number Publication date
DE59800880D1 (de) 2001-07-26
EP0890656A1 (fr) 1999-01-13
DE19729984A1 (de) 1999-01-14
ATE202385T1 (de) 2001-07-15

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